/*
 * Copyright (c) 2009 Duy Nguyen
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Authors: Duy Nguyen <duy@soe.ucsc.edu>
 *          Matías Richart <mrichart@fing.edu.uy>
 *
 * Some Comments:
 *
 * 1) Segment Size is declared for completeness but not used  because it has
 *    to do more with the requirement of the specific hardware.
 *
 * 2) By default, Minstrel applies the multi-rate retry (the core of Minstrel
 *    algorithm). Otherwise, please use ConstantRateWifiManager instead.
 *
 * https://wireless.wiki.kernel.org/en/developers/documentation/mac80211/ratecontrol/minstrel
 */

#include "minstrel-wifi-manager.h"

#include "ns3/log.h"
#include "ns3/packet.h"
#include "ns3/random-variable-stream.h"
#include "ns3/simulator.h"
#include "ns3/wifi-mac.h"
#include "ns3/wifi-phy.h"
#include "ns3/wifi-psdu.h"

#include <iomanip>
#include <limits>

#define Min(a, b) ((a < b) ? a : b)

namespace ns3
{

NS_LOG_COMPONENT_DEFINE("MinstrelWifiManager");

NS_OBJECT_ENSURE_REGISTERED(MinstrelWifiManager);

TypeId
MinstrelWifiManager::GetTypeId()
{
    static TypeId tid =
        TypeId("ns3::MinstrelWifiManager")
            .SetParent<WifiRemoteStationManager>()
            .SetGroupName("Wifi")
            .AddConstructor<MinstrelWifiManager>()
            .AddAttribute("UpdateStatistics",
                          "The interval between updating statistics table",
                          TimeValue(Seconds(0.1)),
                          MakeTimeAccessor(&MinstrelWifiManager::m_updateStats),
                          MakeTimeChecker())
            .AddAttribute("LookAroundRate",
                          "The percentage to try other rates",
                          UintegerValue(10),
                          MakeUintegerAccessor(&MinstrelWifiManager::m_lookAroundRate),
                          MakeUintegerChecker<uint8_t>())
            .AddAttribute("EWMA",
                          "EWMA level",
                          UintegerValue(75),
                          MakeUintegerAccessor(&MinstrelWifiManager::m_ewmaLevel),
                          MakeUintegerChecker<uint8_t>())
            .AddAttribute("SampleColumn",
                          "The number of columns used for sampling",
                          UintegerValue(10),
                          MakeUintegerAccessor(&MinstrelWifiManager::m_sampleCol),
                          MakeUintegerChecker<uint8_t>())
            .AddAttribute("PacketLength",
                          "The packet length used for calculating mode TxTime",
                          UintegerValue(1200),
                          MakeUintegerAccessor(&MinstrelWifiManager::m_pktLen),
                          MakeUintegerChecker<uint32_t>())
            .AddAttribute("PrintStats",
                          "Print statistics table",
                          BooleanValue(false),
                          MakeBooleanAccessor(&MinstrelWifiManager::m_printStats),
                          MakeBooleanChecker())
            .AddAttribute("PrintSamples",
                          "Print samples table",
                          BooleanValue(false),
                          MakeBooleanAccessor(&MinstrelWifiManager::m_printSamples),
                          MakeBooleanChecker())
            .AddTraceSource("Rate",
                            "Traced value for rate changes (b/s)",
                            MakeTraceSourceAccessor(&MinstrelWifiManager::m_currentRate),
                            "ns3::TracedValueCallback::Uint64");
    return tid;
}

MinstrelWifiManager::MinstrelWifiManager()
    : WifiRemoteStationManager(),
      m_currentRate(0)
{
    NS_LOG_FUNCTION(this);
    m_uniformRandomVariable = CreateObject<UniformRandomVariable>();
}

MinstrelWifiManager::~MinstrelWifiManager()
{
    NS_LOG_FUNCTION(this);
}

void
MinstrelWifiManager::SetupPhy(const Ptr<WifiPhy> phy)
{
    NS_LOG_FUNCTION(this << phy);
    for (const auto& mode : phy->GetModeList())
    {
        WifiTxVector txVector;
        txVector.SetMode(mode);
        txVector.SetPreambleType(WIFI_PREAMBLE_LONG);
        AddCalcTxTime(mode, phy->CalculateTxDuration(m_pktLen, txVector, phy->GetPhyBand()));
    }
    WifiRemoteStationManager::SetupPhy(phy);
}

void
MinstrelWifiManager::SetupMac(const Ptr<WifiMac> mac)
{
    NS_LOG_FUNCTION(this << mac);
    WifiRemoteStationManager::SetupMac(mac);
}

void
MinstrelWifiManager::DoInitialize()
{
    NS_LOG_FUNCTION(this);
    if (GetHtSupported())
    {
        NS_FATAL_ERROR("WifiRemoteStationManager selected does not support HT rates");
    }
    if (GetVhtSupported())
    {
        NS_FATAL_ERROR("WifiRemoteStationManager selected does not support VHT rates");
    }
    if (GetHeSupported())
    {
        NS_FATAL_ERROR("WifiRemoteStationManager selected does not support HE rates");
    }
}

int64_t
MinstrelWifiManager::AssignStreams(int64_t stream)
{
    NS_LOG_FUNCTION(this << stream);
    m_uniformRandomVariable->SetStream(stream);
    return 1;
}

Time
MinstrelWifiManager::GetCalcTxTime(WifiMode mode) const
{
    NS_LOG_FUNCTION(this << mode);
    auto it = m_calcTxTime.find(mode);
    NS_ASSERT(it != m_calcTxTime.end());
    return it->second;
}

void
MinstrelWifiManager::AddCalcTxTime(WifiMode mode, Time t)
{
    NS_LOG_FUNCTION(this << mode << t);
    m_calcTxTime.insert(std::make_pair(mode, t));
}

WifiRemoteStation*
MinstrelWifiManager::DoCreateStation() const
{
    NS_LOG_FUNCTION(this);
    auto station = new MinstrelWifiRemoteStation();

    station->m_nextStatsUpdate = Simulator::Now() + m_updateStats;
    station->m_col = 0;
    station->m_index = 0;
    station->m_maxTpRate = 0;
    station->m_maxTpRate2 = 0;
    station->m_maxProbRate = 0;
    station->m_nModes = 0;
    station->m_totalPacketsCount = 0;
    station->m_samplePacketsCount = 0;
    station->m_isSampling = false;
    station->m_sampleRate = 0;
    station->m_sampleDeferred = false;
    station->m_shortRetry = 0;
    station->m_longRetry = 0;
    station->m_retry = 0;
    station->m_txrate = 0;
    station->m_initialized = false;

    return station;
}

void
MinstrelWifiManager::CheckInit(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);
    if (!station->m_initialized && GetNSupported(station) > 1)
    {
        // Note: we appear to be doing late initialization of the table
        // to make sure that the set of supported rates has been initialized
        // before we perform our own initialization.
        station->m_nModes = GetNSupported(station);
        station->m_minstrelTable = MinstrelRate(station->m_nModes);
        station->m_sampleTable = SampleRate(station->m_nModes, std::vector<uint8_t>(m_sampleCol));
        InitSampleTable(station);
        RateInit(station);
        station->m_initialized = true;
    }
}

/**
 *
 * Retry Chain table is implemented here
 *
 * Try |         LOOKAROUND RATE              | NORMAL RATE
 *     | random < best    | random > best     |
 * --------------------------------------------------------------
 *  1  | Best throughput  | Random rate       | Best throughput
 *  2  | Random rate      | Best throughput   | Next best throughput
 *  3  | Best probability | Best probability  | Best probability
 *  4  | Lowest base rate | Lowest base rate  | Lowest base rate
 *
 * Note: For clarity, multiple blocks of if's and else's are used
 * After failing max retry times, DoReportFinalDataFailed will be called
 */
void
MinstrelWifiManager::UpdateRate(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);
    station->m_longRetry++;
    station->m_minstrelTable[station->m_txrate].numRateAttempt++;

    NS_LOG_DEBUG("DoReportDataFailed " << station << " rate " << station->m_txrate << " longRetry "
                                       << station->m_longRetry);

    // for normal rate, we're not currently sampling random rates
    if (!station->m_isSampling)
    {
        NS_LOG_DEBUG("Failed with normal rate: current="
                     << station->m_txrate << ", sample=" << station->m_sampleRate
                     << ", maxTp=" << station->m_maxTpRate << ", maxTp2=" << station->m_maxTpRate2
                     << ", maxProb=" << station->m_maxProbRate);
        // use best throughput rate
        if (station->m_longRetry <
            station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount)
        {
            NS_LOG_DEBUG(" More retries left for the maximum throughput rate.");
            station->m_txrate = station->m_maxTpRate;
        }

        // use second best throughput rate
        else if (station->m_longRetry <=
                 (station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount +
                  station->m_minstrelTable[station->m_maxTpRate2].adjustedRetryCount))
        {
            NS_LOG_DEBUG(" More retries left for the second maximum throughput rate.");
            station->m_txrate = station->m_maxTpRate2;
        }

        // use best probability rate
        else if (station->m_longRetry <=
                 (station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount +
                  station->m_minstrelTable[station->m_maxTpRate2].adjustedRetryCount +
                  station->m_minstrelTable[station->m_maxProbRate].adjustedRetryCount))
        {
            NS_LOG_DEBUG(" More retries left for the maximum probability rate.");
            station->m_txrate = station->m_maxProbRate;
        }

        // use lowest base rate
        else if (station->m_longRetry >
                 (station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount +
                  station->m_minstrelTable[station->m_maxTpRate2].adjustedRetryCount +
                  station->m_minstrelTable[station->m_maxProbRate].adjustedRetryCount))
        {
            NS_LOG_DEBUG(" More retries left for the base rate.");
            station->m_txrate = 0;
        }
    }

    // for look-around rate, we're currently sampling random rates
    else
    {
        NS_LOG_DEBUG("Failed with look around rate: current="
                     << station->m_txrate << ", sample=" << station->m_sampleRate
                     << ", maxTp=" << station->m_maxTpRate << ", maxTp2=" << station->m_maxTpRate2
                     << ", maxProb=" << station->m_maxProbRate);
        // current sampling rate is slower than the current best rate
        if (station->m_sampleDeferred)
        {
            NS_LOG_DEBUG("Look around rate is slower than the maximum throughput rate.");
            // use best throughput rate
            if (station->m_longRetry <
                station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount)
            {
                NS_LOG_DEBUG(" More retries left for the maximum throughput rate.");
                station->m_txrate = station->m_maxTpRate;
            }

            // use random rate
            else if (station->m_longRetry <=
                     (station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount +
                      station->m_minstrelTable[station->m_sampleRate].adjustedRetryCount))
            {
                NS_LOG_DEBUG(" More retries left for the sampling rate.");
                station->m_txrate = station->m_sampleRate;
            }

            // use max probability rate
            else if (station->m_longRetry <=
                     (station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount +
                      station->m_minstrelTable[station->m_sampleRate].adjustedRetryCount +
                      station->m_minstrelTable[station->m_maxProbRate].adjustedRetryCount))
            {
                NS_LOG_DEBUG(" More retries left for the maximum probability rate.");
                station->m_txrate = station->m_maxProbRate;
            }

            // use lowest base rate
            else if (station->m_longRetry >
                     (station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount +
                      station->m_minstrelTable[station->m_sampleRate].adjustedRetryCount +
                      station->m_minstrelTable[station->m_maxProbRate].adjustedRetryCount))
            {
                NS_LOG_DEBUG(" More retries left for the base rate.");
                station->m_txrate = 0;
            }
        }
        // current sampling rate is better than current best rate
        else
        {
            NS_LOG_DEBUG("Look around rate is faster than the maximum throughput rate.");
            // use random rate
            if (station->m_longRetry <
                station->m_minstrelTable[station->m_sampleRate].adjustedRetryCount)
            {
                NS_LOG_DEBUG(" More retries left for the sampling rate.");
                station->m_txrate = station->m_sampleRate;
            }

            // use the best throughput rate
            else if (station->m_longRetry <=
                     (station->m_minstrelTable[station->m_sampleRate].adjustedRetryCount +
                      station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount))
            {
                NS_LOG_DEBUG(" More retries left for the maximum throughput rate.");
                station->m_txrate = station->m_maxTpRate;
            }

            // use the best probability rate
            else if (station->m_longRetry <=
                     (station->m_minstrelTable[station->m_sampleRate].adjustedRetryCount +
                      station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount +
                      station->m_minstrelTable[station->m_maxProbRate].adjustedRetryCount))
            {
                NS_LOG_DEBUG(" More retries left for the maximum probability rate.");
                station->m_txrate = station->m_maxProbRate;
            }

            // use the lowest base rate
            else if (station->m_longRetry >
                     (station->m_minstrelTable[station->m_sampleRate].adjustedRetryCount +
                      station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount +
                      station->m_minstrelTable[station->m_maxProbRate].adjustedRetryCount))
            {
                NS_LOG_DEBUG(" More retries left for the base rate.");
                station->m_txrate = 0;
            }
        }
    }
}

WifiTxVector
MinstrelWifiManager::GetDataTxVector(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);
    auto channelWidth = GetChannelWidth(station);
    if (channelWidth > MHz_u{20} && channelWidth != MHz_u{22})
    {
        channelWidth = MHz_u{20};
    }
    if (!station->m_initialized)
    {
        CheckInit(station);
    }
    WifiMode mode = GetSupported(station, station->m_txrate);
    uint64_t rate = mode.GetDataRate(channelWidth);
    if (m_currentRate != rate && !station->m_isSampling)
    {
        NS_LOG_DEBUG("New datarate: " << rate);
        m_currentRate = rate;
    }
    return WifiTxVector(
        mode,
        GetDefaultTxPowerLevel(),
        GetPreambleForTransmission(mode.GetModulationClass(), GetShortPreambleEnabled()),
        NanoSeconds(800),
        1,
        1,
        0,
        channelWidth,
        GetAggregation(station));
}

WifiTxVector
MinstrelWifiManager::GetRtsTxVector(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);
    NS_LOG_DEBUG("DoGetRtsMode m_txrate=" << station->m_txrate);
    auto channelWidth = GetChannelWidth(station);
    if (channelWidth > MHz_u{20} && channelWidth != MHz_u{22})
    {
        channelWidth = MHz_u{20};
    }
    WifiMode mode;
    if (!GetUseNonErpProtection())
    {
        mode = GetSupported(station, 0);
    }
    else
    {
        mode = GetNonErpSupported(station, 0);
    }
    return WifiTxVector(
        mode,
        GetDefaultTxPowerLevel(),
        GetPreambleForTransmission(mode.GetModulationClass(), GetShortPreambleEnabled()),
        NanoSeconds(800),
        1,
        1,
        0,
        channelWidth,
        GetAggregation(station));
}

uint32_t
MinstrelWifiManager::CountRetries(MinstrelWifiRemoteStation* station)
{
    if (!station->m_isSampling)
    {
        return station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount +
               station->m_minstrelTable[station->m_maxTpRate2].adjustedRetryCount +
               station->m_minstrelTable[station->m_maxProbRate].adjustedRetryCount +
               station->m_minstrelTable[0].adjustedRetryCount;
    }
    else
    {
        return station->m_minstrelTable[station->m_sampleRate].adjustedRetryCount +
               station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount +
               station->m_minstrelTable[station->m_maxProbRate].adjustedRetryCount +
               station->m_minstrelTable[0].adjustedRetryCount;
    }
}

uint16_t
MinstrelWifiManager::FindRate(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);

    if (station->m_totalPacketsCount == 0)
    {
        return 0;
    }

    uint16_t idx = 0;
    NS_LOG_DEBUG("Total: " << station->m_totalPacketsCount
                           << "  Sample: " << station->m_samplePacketsCount
                           << "  Deferred: " << station->m_numSamplesDeferred);

    int delta = (station->m_totalPacketsCount * m_lookAroundRate / 100) -
                (station->m_samplePacketsCount + station->m_numSamplesDeferred / 2);

    NS_LOG_DEBUG("Decide sampling. Delta: " << delta << " lookAroundRatio: " << m_lookAroundRate);

    /* delta < 0: no sampling required */
    if (delta >= 0)
    {
        NS_LOG_DEBUG("Search next sampling rate");
        uint8_t ratesSupported = station->m_nModes;
        if (delta > ratesSupported * 2)
        {
            /* From Linux implementation:
             * With multi-rate retry, not every planned sample
             * attempt actually gets used, due to the way the retry
             * chain is set up - [max_tp,sample,prob,lowest] for
             * sample_rate < max_tp.
             *
             * If there's too much sampling backlog and the link
             * starts getting worse, minstrel would start bursting
             * out lots of sampling frames, which would result
             * in a large throughput loss. */
            station->m_samplePacketsCount += (delta - ratesSupported * 2);
        }

        // now go through the table and find an index rate
        idx = GetNextSample(station);

        NS_LOG_DEBUG("Sample rate = " << idx << "(" << GetSupported(station, idx) << ")");

        // error check
        if (idx >= station->m_nModes)
        {
            NS_LOG_DEBUG("ALERT!!! ERROR");
        }

        // set the rate that we're currently sampling
        station->m_sampleRate = idx;

        /* From Linux implementation:
         * Decide if direct ( 1st MRR stage) or indirect (2nd MRR stage)
         * rate sampling method should be used.
         * Respect such rates that are not sampled for 20 iterations.
         */
        if ((station->m_minstrelTable[idx].perfectTxTime >
             station->m_minstrelTable[station->m_maxTpRate].perfectTxTime) &&
            (station->m_minstrelTable[idx].numSamplesSkipped < 20))
        {
            // If the rate is slower and we have sample it enough, defer to second stage
            station->m_sampleDeferred = true;
            station->m_numSamplesDeferred++;

            // set flag that we are currently sampling
            station->m_isSampling = true;
        }
        else
        {
            // if samplieLimit is zero, then don't sample this rate
            if (!station->m_minstrelTable[idx].sampleLimit)
            {
                idx = station->m_maxTpRate;
                station->m_isSampling = false;
            }
            else
            {
                // set flag that we are currently sampling
                station->m_isSampling = true;
                if (station->m_minstrelTable[idx].sampleLimit > 0)
                {
                    station->m_minstrelTable[idx].sampleLimit--;
                }
            }
        }

        // using the best rate instead
        if (station->m_sampleDeferred)
        {
            NS_LOG_DEBUG("The next look around rate is slower than the maximum throughput rate, "
                         "continue with the maximum throughput rate: "
                         << station->m_maxTpRate << "("
                         << GetSupported(station, station->m_maxTpRate) << ")");
            idx = station->m_maxTpRate;
        }
    }
    // continue using the best rate
    else
    {
        NS_LOG_DEBUG("Continue using the maximum throughput rate: "
                     << station->m_maxTpRate << "(" << GetSupported(station, station->m_maxTpRate)
                     << ")");
        idx = station->m_maxTpRate;
    }

    NS_LOG_DEBUG("Rate = " << idx << "(" << GetSupported(station, idx) << ")");

    return idx;
}

void
MinstrelWifiManager::UpdateStats(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);
    if (Simulator::Now() < station->m_nextStatsUpdate)
    {
        return;
    }

    if (!station->m_initialized)
    {
        return;
    }
    NS_LOG_FUNCTION(this);
    station->m_nextStatsUpdate = Simulator::Now() + m_updateStats;
    NS_LOG_DEBUG("Next update at " << station->m_nextStatsUpdate);
    NS_LOG_DEBUG("Currently using rate: " << station->m_txrate << " ("
                                          << GetSupported(station, station->m_txrate) << ")");

    Time txTime;
    uint32_t tempProb;

    NS_LOG_DEBUG("Index-Rate\t\tAttempt\tSuccess");
    for (uint8_t i = 0; i < station->m_nModes; i++)
    {
        // calculate the perfect TX time for this rate
        txTime = station->m_minstrelTable[i].perfectTxTime;

        // just for initialization
        if (txTime.GetMicroSeconds() == 0)
        {
            txTime = Seconds(1);
        }

        NS_LOG_DEBUG(+i << " " << GetSupported(station, i) << "\t"
                        << station->m_minstrelTable[i].numRateAttempt << "\t"
                        << station->m_minstrelTable[i].numRateSuccess);

        // if we've attempted something
        if (station->m_minstrelTable[i].numRateAttempt)
        {
            station->m_minstrelTable[i].numSamplesSkipped = 0;
            /**
             * calculate the probability of success
             * assume probability scales from 0 to 18000
             */
            tempProb = (station->m_minstrelTable[i].numRateSuccess * 18000) /
                       station->m_minstrelTable[i].numRateAttempt;

            // bookkeeping
            station->m_minstrelTable[i].prob = tempProb;

            if (station->m_minstrelTable[i].successHist == 0)
            {
                station->m_minstrelTable[i].ewmaProb = tempProb;
            }
            else
            {
                // EWMA probability (cast for gcc 3.4 compatibility)
                tempProb = ((tempProb * (100 - m_ewmaLevel)) +
                            (station->m_minstrelTable[i].ewmaProb * m_ewmaLevel)) /
                           100;

                station->m_minstrelTable[i].ewmaProb = tempProb;
            }

            // calculating throughput
            station->m_minstrelTable[i].throughput =
                tempProb * static_cast<uint32_t>(1000000 / txTime.GetMicroSeconds());
        }
        else
        {
            station->m_minstrelTable[i].numSamplesSkipped++;
        }

        // bookkeeping
        station->m_minstrelTable[i].successHist += station->m_minstrelTable[i].numRateSuccess;
        station->m_minstrelTable[i].attemptHist += station->m_minstrelTable[i].numRateAttempt;
        station->m_minstrelTable[i].prevNumRateSuccess = station->m_minstrelTable[i].numRateSuccess;
        station->m_minstrelTable[i].prevNumRateAttempt = station->m_minstrelTable[i].numRateAttempt;
        station->m_minstrelTable[i].numRateSuccess = 0;
        station->m_minstrelTable[i].numRateAttempt = 0;

        // Sample less often below 10% and  above 95% of success
        if ((station->m_minstrelTable[i].ewmaProb > 17100) ||
            (station->m_minstrelTable[i].ewmaProb < 1800))
        {
            /**
             * See:
             * http://wireless.kernel.org/en/developers/Documentation/mac80211/RateControl/minstrel/
             *
             * Analysis of information showed that the system was sampling too hard at some rates.
             * For those rates that never work (54mb, 500m range) there is no point in retrying 10
             * sample packets (< 6 ms time). Consequently, for the very low probability rates, we
             * try at most twice when fails and not sample more than 4 times.
             */
            if (station->m_minstrelTable[i].retryCount > 2)
            {
                station->m_minstrelTable[i].adjustedRetryCount = 2;
            }
            station->m_minstrelTable[i].sampleLimit = 4;
        }
        else
        {
            // no sampling limit.
            station->m_minstrelTable[i].sampleLimit = -1;
            station->m_minstrelTable[i].adjustedRetryCount = station->m_minstrelTable[i].retryCount;
        }

        // if it's 0 allow two retries.
        if (station->m_minstrelTable[i].adjustedRetryCount == 0)
        {
            station->m_minstrelTable[i].adjustedRetryCount = 2;
        }
    }

    NS_LOG_DEBUG("Attempt/success reset to 0");

    uint32_t max_tp = 0;
    uint8_t index_max_tp = 0;
    uint8_t index_max_tp2 = 0;

    // go find max throughput, second maximum throughput, high probability of success
    NS_LOG_DEBUG(
        "Finding the maximum throughput, second maximum throughput, and highest probability");
    NS_LOG_DEBUG("Index-Rate\t\tT-put\tEWMA");
    for (uint8_t i = 0; i < station->m_nModes; i++)
    {
        NS_LOG_DEBUG(+i << " " << GetSupported(station, i) << "\t"
                        << station->m_minstrelTable[i].throughput << "\t"
                        << station->m_minstrelTable[i].ewmaProb);

        if (max_tp < station->m_minstrelTable[i].throughput)
        {
            index_max_tp = i;
            max_tp = station->m_minstrelTable[i].throughput;
        }
    }

    max_tp = 0;
    // find the second highest max
    for (uint8_t i = 0; i < station->m_nModes; i++)
    {
        if ((i != index_max_tp) && (max_tp < station->m_minstrelTable[i].throughput))
        {
            index_max_tp2 = i;
            max_tp = station->m_minstrelTable[i].throughput;
        }
    }

    uint32_t max_prob = 0;
    uint8_t index_max_prob = 0;
    for (uint8_t i = 0; i < station->m_nModes; i++)
    {
        if ((station->m_minstrelTable[i].ewmaProb >= 95 * 180 &&
             station->m_minstrelTable[i].throughput >=
                 station->m_minstrelTable[index_max_prob].throughput) ||
            (station->m_minstrelTable[i].ewmaProb >= max_prob))
        {
            index_max_prob = i;
            max_prob = station->m_minstrelTable[i].ewmaProb;
        }
    }

    station->m_maxTpRate = index_max_tp;
    station->m_maxTpRate2 = index_max_tp2;
    station->m_maxProbRate = index_max_prob;

    if (index_max_tp > station->m_txrate)
    {
        station->m_txrate = index_max_tp;
    }

    NS_LOG_DEBUG("max throughput=" << +index_max_tp << "(" << GetSupported(station, index_max_tp)
                                   << ")\tsecond max throughput=" << +index_max_tp2 << "("
                                   << GetSupported(station, index_max_tp2)
                                   << ")\tmax prob=" << +index_max_prob << "("
                                   << GetSupported(station, index_max_prob) << ")");
    if (m_printStats)
    {
        PrintTable(station);
    }
    if (m_printSamples)
    {
        PrintSampleTable(station);
    }
}

void
MinstrelWifiManager::DoReportRxOk(WifiRemoteStation* st, double rxSnr, WifiMode txMode)
{
    NS_LOG_FUNCTION(this << st << rxSnr << txMode);
    NS_LOG_DEBUG("DoReportRxOk m_txrate=" << static_cast<MinstrelWifiRemoteStation*>(st)->m_txrate);
}

void
MinstrelWifiManager::DoReportRtsFailed(WifiRemoteStation* st)
{
    NS_LOG_FUNCTION(this << st);
    auto station = static_cast<MinstrelWifiRemoteStation*>(st);
    NS_LOG_DEBUG("DoReportRtsFailed m_txrate=" << station->m_txrate);
    station->m_shortRetry++;
}

void
MinstrelWifiManager::DoReportRtsOk(WifiRemoteStation* st,
                                   double ctsSnr,
                                   WifiMode ctsMode,
                                   double rtsSnr)
{
    NS_LOG_FUNCTION(this << st << ctsSnr << ctsMode << rtsSnr);
}

void
MinstrelWifiManager::DoReportFinalRtsFailed(WifiRemoteStation* st)
{
    NS_LOG_FUNCTION(this << st);
    auto station = static_cast<MinstrelWifiRemoteStation*>(st);
    UpdateRetry(station);
}

void
MinstrelWifiManager::DoReportDataFailed(WifiRemoteStation* st)
{
    NS_LOG_FUNCTION(this << st);
    auto station = static_cast<MinstrelWifiRemoteStation*>(st);
    NS_LOG_DEBUG("DoReportDataFailed " << station << "\t rate " << station->m_txrate
                                       << "\tlongRetry \t" << station->m_longRetry);
    CheckInit(station);
    if (!station->m_initialized)
    {
        return;
    }

    UpdateRate(station);
}

void
MinstrelWifiManager::DoReportDataOk(WifiRemoteStation* st,
                                    double ackSnr,
                                    WifiMode ackMode,
                                    double dataSnr,
                                    MHz_u dataChannelWidth,
                                    uint8_t dataNss)
{
    NS_LOG_FUNCTION(this << st << ackSnr << ackMode << dataSnr << dataChannelWidth << +dataNss);
    auto station = static_cast<MinstrelWifiRemoteStation*>(st);

    CheckInit(station);
    if (!station->m_initialized)
    {
        return;
    }

    NS_LOG_DEBUG("DoReportDataOk m_txrate = "
                 << station->m_txrate
                 << ", attempt = " << station->m_minstrelTable[station->m_txrate].numRateAttempt
                 << ", success = " << station->m_minstrelTable[station->m_txrate].numRateSuccess
                 << " (before update).");

    station->m_minstrelTable[station->m_txrate].numRateSuccess++;
    station->m_minstrelTable[station->m_txrate].numRateAttempt++;

    UpdatePacketCounters(station);

    NS_LOG_DEBUG("DoReportDataOk m_txrate = "
                 << station->m_txrate
                 << ", attempt = " << station->m_minstrelTable[station->m_txrate].numRateAttempt
                 << ", success = " << station->m_minstrelTable[station->m_txrate].numRateSuccess
                 << " (after update).");

    UpdateRetry(station);
    UpdateStats(station);

    if (station->m_nModes >= 1)
    {
        station->m_txrate = FindRate(station);
    }
    NS_LOG_DEBUG("Next rate to use TxRate = " << station->m_txrate);
}

void
MinstrelWifiManager::DoReportFinalDataFailed(WifiRemoteStation* st)
{
    NS_LOG_FUNCTION(this << st);
    auto station = static_cast<MinstrelWifiRemoteStation*>(st);

    CheckInit(station);
    if (!station->m_initialized)
    {
        return;
    }

    NS_LOG_DEBUG("DoReportFinalDataFailed m_txrate = "
                 << station->m_txrate
                 << ", attempt = " << station->m_minstrelTable[station->m_txrate].numRateAttempt
                 << ", success = " << station->m_minstrelTable[station->m_txrate].numRateSuccess
                 << " (before update).");

    UpdatePacketCounters(station);

    UpdateRetry(station);
    UpdateStats(station);

    NS_LOG_DEBUG("DoReportFinalDataFailed m_txrate = "
                 << station->m_txrate
                 << ", attempt = " << station->m_minstrelTable[station->m_txrate].numRateAttempt
                 << ", success = " << station->m_minstrelTable[station->m_txrate].numRateSuccess
                 << " (after update).");

    if (station->m_nModes >= 1)
    {
        station->m_txrate = FindRate(station);
    }
    NS_LOG_DEBUG("Next rate to use TxRate = " << station->m_txrate);
}

void
MinstrelWifiManager::UpdatePacketCounters(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);

    station->m_totalPacketsCount++;
    // If it is a sampling frame and the sampleRate was used, increase counter
    if (station->m_isSampling &&
        (!station->m_sampleDeferred ||
         station->m_longRetry >= station->m_minstrelTable[station->m_maxTpRate].adjustedRetryCount))
    {
        station->m_samplePacketsCount++;
    }

    if (station->m_numSamplesDeferred > 0)
    {
        station->m_numSamplesDeferred--;
    }

    if (station->m_totalPacketsCount == ~0)
    {
        station->m_numSamplesDeferred = 0;
        station->m_samplePacketsCount = 0;
        station->m_totalPacketsCount = 0;
    }
    station->m_isSampling = false;
    station->m_sampleDeferred = false;
}

void
MinstrelWifiManager::UpdateRetry(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);
    station->m_retry = station->m_shortRetry + station->m_longRetry;
    station->m_shortRetry = 0;
    station->m_longRetry = 0;
}

WifiTxVector
MinstrelWifiManager::DoGetDataTxVector(WifiRemoteStation* st, MHz_u allowedWidth)
{
    NS_LOG_FUNCTION(this << st << allowedWidth);
    auto station = static_cast<MinstrelWifiRemoteStation*>(st);
    return GetDataTxVector(station);
}

WifiTxVector
MinstrelWifiManager::DoGetRtsTxVector(WifiRemoteStation* st)
{
    NS_LOG_FUNCTION(this << st);
    auto station = static_cast<MinstrelWifiRemoteStation*>(st);
    return GetRtsTxVector(station);
}

std::list<Ptr<WifiMpdu>>
MinstrelWifiManager::DoGetMpdusToDropOnTxFailure(WifiRemoteStation* station, Ptr<WifiPsdu> psdu)
{
    NS_LOG_FUNCTION(this << *psdu);

    std::list<Ptr<WifiMpdu>> mpdusToDrop;

    for (const auto& mpdu : *PeekPointer(psdu))
    {
        if (!DoNeedRetransmission(station,
                                  mpdu->GetPacket(),
                                  (mpdu->GetRetryCount() < GetMac()->GetFrameRetryLimit())))
        {
            // this MPDU needs to be dropped
            mpdusToDrop.push_back(mpdu);
        }
    }

    return mpdusToDrop;
}

bool
MinstrelWifiManager::DoNeedRetransmission(WifiRemoteStation* st,
                                          Ptr<const Packet> packet,
                                          bool normally)
{
    NS_LOG_FUNCTION(this << st << packet << normally);
    auto station = static_cast<MinstrelWifiRemoteStation*>(st);

    CheckInit(station);
    if (!station->m_initialized)
    {
        return normally;
    }
    if (station->m_longRetry >= CountRetries(station))
    {
        NS_LOG_DEBUG("No re-transmission allowed. Retries: "
                     << station->m_longRetry << " Max retries: " << CountRetries(station));
        return false;
    }
    else
    {
        NS_LOG_DEBUG("Re-transmit. Retries: " << station->m_longRetry
                                              << " Max retries: " << CountRetries(station));
        return true;
    }
}

uint16_t
MinstrelWifiManager::GetNextSample(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);
    uint16_t bitrate;
    bitrate = station->m_sampleTable[station->m_index][station->m_col];
    station->m_index++;

    // bookkeeping for m_index and m_col variables
    NS_ABORT_MSG_IF(station->m_nModes < 2, "Integer overflow detected");
    if (station->m_index > station->m_nModes - 2)
    {
        station->m_index = 0;
        station->m_col++;
        if (station->m_col >= m_sampleCol)
        {
            station->m_col = 0;
        }
    }
    return bitrate;
}

void
MinstrelWifiManager::RateInit(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);
    for (uint8_t i = 0; i < station->m_nModes; i++)
    {
        NS_LOG_DEBUG("Initializing rate index " << +i << " " << GetSupported(station, i));
        station->m_minstrelTable[i].numRateAttempt = 0;
        station->m_minstrelTable[i].numRateSuccess = 0;
        station->m_minstrelTable[i].prevNumRateSuccess = 0;
        station->m_minstrelTable[i].prevNumRateAttempt = 0;
        station->m_minstrelTable[i].successHist = 0;
        station->m_minstrelTable[i].attemptHist = 0;
        station->m_minstrelTable[i].numSamplesSkipped = 0;
        station->m_minstrelTable[i].prob = 0;
        station->m_minstrelTable[i].ewmaProb = 0;
        station->m_minstrelTable[i].throughput = 0;
        station->m_minstrelTable[i].perfectTxTime = GetCalcTxTime(GetSupported(station, i));
        NS_LOG_DEBUG(" perfectTxTime = " << station->m_minstrelTable[i].perfectTxTime);
        station->m_minstrelTable[i].retryCount = 1;
        station->m_minstrelTable[i].adjustedRetryCount = 1;
        // Emulating minstrel.c::ath_rate_ctl_reset
        // We only check from 2 to 10 retries. This guarantee that
        // at least one retry is permitted.
        Time totalTxTimeWithGivenRetries; // tx_time in minstrel.c
        NS_LOG_DEBUG(" Calculating the number of retries");
        for (uint32_t retries = 2; retries < 11; retries++)
        {
            NS_LOG_DEBUG("  Checking " << retries << " retries");
            totalTxTimeWithGivenRetries =
                CalculateTimeUnicastPacket(station->m_minstrelTable[i].perfectTxTime, 0, retries);
            NS_LOG_DEBUG("   totalTxTimeWithGivenRetries = " << totalTxTimeWithGivenRetries);
            if (totalTxTimeWithGivenRetries > MilliSeconds(6))
            {
                break;
            }
            station->m_minstrelTable[i].sampleLimit = -1;
            station->m_minstrelTable[i].retryCount = retries;
            station->m_minstrelTable[i].adjustedRetryCount = retries;
        }
    }
    UpdateStats(station);
}

Time
MinstrelWifiManager::CalculateTimeUnicastPacket(Time dataTransmissionTime,
                                                uint32_t shortRetries,
                                                uint32_t longRetries)
{
    NS_LOG_FUNCTION(this << dataTransmissionTime << shortRetries << longRetries);
    // See rc80211_minstrel.c

    // First transmission (Data + Ack timeout)
    Time tt = dataTransmissionTime + GetPhy()->GetSifs() + GetPhy()->GetAckTxTime();

    uint32_t cwMax = 1023;
    uint32_t cw = 31;
    for (uint32_t retry = 0; retry < longRetries; retry++)
    {
        // Add one re-transmission (Data + Ack timeout)
        tt += dataTransmissionTime + GetPhy()->GetSifs() + GetPhy()->GetAckTxTime();

        // Add average back off (half the current contention window)
        tt += (cw / 2.0) * GetPhy()->GetSlot();

        // Update contention window
        cw = std::min(cwMax, (cw + 1) * 2);
    }

    return tt;
}

void
MinstrelWifiManager::InitSampleTable(MinstrelWifiRemoteStation* station)
{
    NS_LOG_FUNCTION(this << station);
    station->m_col = station->m_index = 0;

    // for off-setting to make rates fall between 0 and nModes
    uint8_t numSampleRates = station->m_nModes;

    uint16_t newIndex;
    for (uint8_t col = 0; col < m_sampleCol; col++)
    {
        for (uint8_t i = 0; i < numSampleRates; i++)
        {
            /**
             * The next two lines basically tries to generate a random number
             * between 0 and the number of available rates
             */
            int uv = m_uniformRandomVariable->GetInteger(0, numSampleRates);
            NS_LOG_DEBUG("InitSampleTable uv: " << uv);
            newIndex = (i + uv) % numSampleRates;

            // this loop is used for filling in other uninitialized places
            while (station->m_sampleTable[newIndex][col] != 0)
            {
                newIndex = (newIndex + 1) % station->m_nModes;
            }
            station->m_sampleTable[newIndex][col] = i;
        }
    }
}

void
MinstrelWifiManager::PrintSampleTable(MinstrelWifiRemoteStation* station) const
{
    uint8_t numSampleRates = station->m_nModes;
    std::stringstream table;
    for (uint8_t i = 0; i < numSampleRates; i++)
    {
        for (uint8_t j = 0; j < m_sampleCol; j++)
        {
            table << station->m_sampleTable[i][j] << "\t";
        }
        table << std::endl;
    }
    NS_LOG_DEBUG(table.str());
}

void
MinstrelWifiManager::PrintTable(MinstrelWifiRemoteStation* station)
{
    if (!station->m_statsFile.is_open())
    {
        std::ostringstream tmp;
        tmp << "minstrel-stats-" << station->m_state->m_address << ".txt";
        station->m_statsFile.open(tmp.str(), std::ios::out);
    }

    station->m_statsFile
        << "best   _______________rate________________    ________statistics________    "
           "________last_______    ______sum-of________\n"
        << "rate  [      name       idx airtime max_tp]  [avg(tp) avg(prob) sd(prob)]  "
           "[prob.|retry|suc|att]  [#success | #attempts]\n";

    uint16_t maxTpRate = station->m_maxTpRate;
    uint16_t maxTpRate2 = station->m_maxTpRate2;
    uint16_t maxProbRate = station->m_maxProbRate;

    for (uint8_t i = 0; i < station->m_nModes; i++)
    {
        RateInfo rate = station->m_minstrelTable[i];

        if (i == maxTpRate)
        {
            station->m_statsFile << 'A';
        }
        else
        {
            station->m_statsFile << ' ';
        }
        if (i == maxTpRate2)
        {
            station->m_statsFile << 'B';
        }
        else
        {
            station->m_statsFile << ' ';
        }
        if (i == maxProbRate)
        {
            station->m_statsFile << 'P';
        }
        else
        {
            station->m_statsFile << ' ';
        }

        float tmpTh = rate.throughput / 100000.0F;
        station->m_statsFile << "   " << std::setw(17) << GetSupported(station, i) << "  "
                             << std::setw(2) << i << "  " << std::setw(4)
                             << rate.perfectTxTime.GetMicroSeconds() << std::setw(8)
                             << "    -----    " << std::setw(8) << tmpTh << "    " << std::setw(3)
                             << rate.ewmaProb / 180 << std::setw(3) << "       ---      "
                             << std::setw(3) << rate.prob / 180 << "     " << std::setw(1)
                             << rate.adjustedRetryCount << "   " << std::setw(3)
                             << rate.prevNumRateSuccess << " " << std::setw(3)
                             << rate.prevNumRateAttempt << "   " << std::setw(9) << rate.successHist
                             << "   " << std::setw(9) << rate.attemptHist << "\n";
    }
    station->m_statsFile << "\nTotal packet count:    ideal "
                         << station->m_totalPacketsCount - station->m_samplePacketsCount
                         << "      lookaround " << station->m_samplePacketsCount << "\n\n";

    station->m_statsFile.flush();
}

} // namespace ns3
